In most prior art motors, the positioning of the rotation shaft is achieved by a heatproof washer or a metallic C-ring. A conventional self-lube bearing fan motor, as shown in FIG. 1, comprises: a base 11, a stator 12, a rotor 13, a bearing 14, an elastic washer 15, and a C-ring 16.
The base 11 is located at the central location of a fan frame 10. The base 11 and the fan frame 10 are integrally formed. In the central location of the base 11 is provided a bearing seat 111. The stator 12 is telescopically fitted on the bearing seat 111 and is fixed relative to the base 11. The stator 12 includes a plurality of coils 121 and a plurality of silicon steel sets 122. The bearing 14 is a self-lube bearing fitted in the bearing seat 111 of the base 11. The rotor 13 includes a hollow cylinder 130 having an open end. The outer wall of the cylinder 130 engages with a fan blade set 134 and on the inner wall of the cylinder 130 is provided a magnet 131. At the central location of the cylinder 130 is provided a rotation shaft 132. A groove 133 is formed near the lower end of the rotation shaft 132. The rotation shaft 132 is received by the bearing 14. The elastic washer 15 is telescopically fitted on the rotation shaft 132 at an upper location thereof to provide an elastic buffer. The C-ring 16 is engaged in the groove 133 near the lower end of the rotation shaft 132 so that rotation shaft 132 is prevented from being disengaged from the base 11.
From the above description, it can be know that in the prior art motor, the C-ring 16 is used to axially position the rotation shaft 132 of the rotor 13 so that when the rotor 13 rotates after the excitation of the coil 121 and generates airflow F1, the C-ring 16 prevents the bearing 14 from disengaging from the base 111 due to the force F2 exerted on the fan blade set 134.
The positioning of the rotation shaft in the aforementioned prior art motor involves the following drawbacks:
1. When the motor operates, the contact wear and friction between the C-ring 16 and bearing 14 are incurred and the life of the motor will be reduced. PA0 2. The friction between the C-ring 16 and the bearing 14 incurs noises or varied rotation speeds. PA0 3. The rotor 13 and the stator 12 are designed with a magnetic bias. However, when the rotor 13 rotates, the rotation shaft 132 is moved by an external force and the equilibrium position of the rotor relative to the stator is determined by the external force. This results in a big problem in motor design.